linux-kernel - Re: [PATCH] usb: gadget: u_serial: Add null pointer check in gserial

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Message-ID: <bf3b5f0a-0a04-2410-9106-1e2957a2ce05@quicinc.com>
Date:   Mon, 22 May 2023 11:19:03 +0530
From:   Prashanth K <quic_prashk@...cinc.com>
To:     Chunfeng Yun <chunfeng.yun@...iatek.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
CC:     Matthias Brugger <matthias.bgg@...il.com>,
        AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>,
        Alan Stern <stern@...land.harvard.edu>,
        Xiu Jianfeng <xiujianfeng@...wei.com>,
        Christophe JAILLET <christophe.jaillet@...adoo.fr>,
        Fabrice Gasnier <fabrice.gasnier@...com>,
        Felipe Balbi <balbi@...nel.org>, <linux-usb@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-mediatek@...ts.infradead.org>,
        Kewu Chen <Kewu.Chen@...iatek.com>, stable <stable@...nel.org>
Subject: Re: [PATCH] usb: gadget: u_serial: Add null pointer check in
 gserial_suspend



On 22-05-23 07:51 am, Chunfeng Yun wrote:
> When gserial_disconnect has already cleared gser->ioport, and the
> suspend triggers afterwards, gserial_suspend gets called, which will
> lead to accessing of gser->ioport and thus causing null pointer
> dereference. Add a null pointer check to prevent it as the bellow
> patch does:
> 5ec63fdbca60 ("usb: gadget: u_serial: Add null pointer check in gserial_resume")
> 
> Fixes: aba3a8d01d62 ("usb: gadget: u_serial: add suspend resume callbacks")
> Cc: stable <stable@...nel.org>
> Signed-off-by: Chunfeng Yun <chunfeng.yun@...iatek.com>
> ---
>   drivers/usb/gadget/function/u_serial.c | 12 ++++++++++--
>   1 file changed, 10 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/usb/gadget/function/u_serial.c b/drivers/usb/gadget/function/u_serial.c
> index a0ca47fbff0f..40ba220cf6d2 100644
> --- a/drivers/usb/gadget/function/u_serial.c
> +++ b/drivers/usb/gadget/function/u_serial.c
> @@ -1420,10 +1420,18 @@ EXPORT_SYMBOL_GPL(gserial_disconnect);
>   
>   void gserial_suspend(struct gserial *gser)
>   {
> -	struct gs_port	*port = gser->ioport;
> +	struct gs_port	*port;
>   	unsigned long	flags;
>   
> -	spin_lock_irqsave(&port->port_lock, flags);
> +	spin_lock_irqsave(&serial_port_lock, flags);
> +	port = gser->ioport;
> +	if (!port) {
> +		spin_unlock_irqrestore(&serial_port_lock, flags);
> +		return;
> +	}
> +
> +	spin_lock(&port->port_lock);
> +	spin_unlock(&serial_port_lock);
>   	port->suspended = true;
>   	spin_unlock_irqrestore(&port->port_lock, flags);
>   }
Hi Chunfeng,

This looks same as the following patch.
https://lore.kernel.org/linux-usb/1683278317-11774-1-git-send-email-quic_prashk@quicinc.com/ 


Regards